MANILA — A day after the United Nations Security Council passed its toughest sanctions against North Korea, Secretary of State Rex W. Tillerson met with his South Korean and Chinese counterparts here in hopes of ratcheting up pressure on Pyongyang.

In a midday conclave on Sunday with Foreign Minister Kang Kyung-wha of South Korea, Mr. Tillerson hailed in his typically understated fashion the United Nations vote, which could cost North Korea nearly $1 billion a year, or about one-third of its foreign earnings.

“It was a good outcome,” Mr. Tillerson said with a smile.

Ms. Kang, sitting across the table from him, could not resist chiming in: “It was a very, very good outcome.”

Despite Mr. Tillerson’s obvious glee, though, the man of the moment here at the annual ministerial meeting of the Association of Southeast Asian Nations, or Asean, was the Chinese foreign minister, Wang Yi, a dashing diplomat who unlike Mr. Tillerson held a news conference and direct talks with Foreign Minister Ri Yong-ho of North Korea.

Mr. Wang said the two had “an intensive conversation,” and in unusually strong terms, he later urged North Korea to show restraint.

“Do not violate the U.N.’s decision or provoke the international society’s good will by conducting missile launching or nuclear tests,” Mr. Wang said.

He also said, “Of course, we would like to urge other parties like the United States and South Korea to stop increasing tensions.”

A year ago, the Chinese were on their heels in this region. An international tribunal in The Hague last July delivered a sweeping rebuke of China’s behavior in the South China Sea, including its construction of artificial islands, finding that its expansive claim to sovereignty over the waters had no legal basis.

The case, brought against China by the Philippines, seemed like a turning point in China’s disputes with a host of regional players, including Brunei, Indonesia, Malaysia, Taiwan and Vietnam.

A few months before that ruling, 12 nations in the Pacific region concluded more than seven years of negotiations by signing the Trans-Pacific Partnership, or TPP, a trade agreement that bound much of Southeast Asia together with the United States and Japan in an economic partnership intended to fight China’s growing economic hegemony in the region.

While China had its own regional trade accord, the United States-led pact had become the preferred agreement, with several nations that had missed out on the initial round of negotiations expressing interest in joining in a second round.

How things have changed.

President Rodrigo Duterte of the Philippines, elected last year, has backed down from his country’s insistence that China abandon the shoals at the heart of the tribunal’s decision, preferring instead to accept significant Chinese economic assistance.

In a news conference on Friday, the Philippine foreign affairs secretary, Alan Peter Cayetano, said the fight with China was not worth the cost.

With the Philippines serving as host to Asean, the country’s about-face lifted a significant cloud over China, with only Vietnam reportedly continuing to insist that the group condemn Beijing’s actions.

Instead, Asean and China adopted a fairly weak negotiating framework for a code of conduct in the South China Sea — several steps removed from anything that could force China to abandon its territorial claims or give up the seven islands it has built in the disputed waters, three of which are equipped with runways and military hardware.

Mr. Wang said the adoption of the framework created a solid foundation for negotiations that could start this year, if “the situation in the South China Sea is generally stable and on the premise that there is no major interference from outside parties,” Reuters reported.

Few believe the framework will lead China to conclude a binding agreement anytime soon.

Perhaps even more important, in his first days in office, President Trump renounced TPP. That action, along with his years of denunciations of the trading policies of Japan and China and a promised “America First” pivot, seemed to many in the region to represent a significant retreat by the United States from its military and economic engagement here, and an important victory for China.

President Barack Obama had lavished attention on the region, where he spent part of his childhood and which has a population of more than 620 million and a collective economy of around $2.4 trillion, the third-largest in Asia behind those of China and Japan.

Geographically astride the world’s busiest and most strategic shipping lanes, the region was the fulcrum of the administration’s rebalancing toward Asia.

Mr. Trump has yet to demonstrate a similar interest or commitment to the region.

In his opening remarks to the conference, Mr. Tillerson sought to put to rest fears that the United States would abandon the region, saying that his multiple meetings with ambassadors were “indicative of the importance that the United States pays and places on this relationship with Asean.”

And while Mr. Tillerson chose not to meet with journalists on Sunday, his top diplomat for the region, Susan A. Thornton, the acting assistant secretary for East Asian and Pacific affairs, said that multiple visits by top administration officials had demonstrated its continued importance to the United States.

“The engagement is not a question,” she said.

Still, Ms. Thornton gave credit to the Chinese for supporting Saturday’s vote in the United Nations against North Korea.

“The fact that the Chinese were helpful and instrumental really in setting up this set of sanctions, this really sweeping set of international sanctions, shows that they realize it’s a huge problem that they need to take on and is a threat to them,” she said.

But Ms. Thornton cautioned that Beijing has often failed to follow through on its promised tough measures against Pyongyang. China accounts for more than 90 percent of North Korea’s external trade, and it has long avoided tough economic sanctions against the North for fear that a collapse of the government would lead to a flood of refugees, as well as the North’s reunification with the South, putting a close American ally directly on China’s border.

“I think we still are going to be watchful as to their implementation of the sanctions,” Ms. Thornton said. “But this is definitely an important step.”

Also on Sunday, Mr. Tillerson met with Foreign Minister Sergey V. Lavrov of Russia. Mr. Lavrov has often spoken expansively and sometimes humorously in the moments before or after meeting top American diplomats. But though he and Mr. Tillerson both smiled and appeared relaxed as they made small talk in the moments before their official meeting, neither said anything to a contingent of journalists briefly ushered into their presence.

In comments that were broadcast on Sunday on Russian television, Mr. Lavrov said that Mr. Tillerson had asked about the details of the reductions in American diplomatic staff members in Russia and that Mr. Lavrov had explained how it would work, according to a translation provided by The Associated Press.

Mr. Lavrov also said Mr. Tillerson had promised to send the United States special envoy for Ukraine, Kurt Volker, to Moscow for discussions.

Correction:

An earlier version of this article referred incorrectly to the foreign minister of South Korea. The minister, Kang Kyung-wha, is a woman.

Correction:

An earlier version of this article misidentified the foreign minister of North Korea. He is Ri Yong-ho, not Ri Su-yong.

A version of this article appears in print on , on Page A8 of the New York edition with the headline: Tillerson Hails U.N. Sanctions as Chinese Minister Rebukes North Korea. Order Reprints | Today’s Paper | Subscribe